Laminated molded body

Abstract

An object of the present invention is to provide a laminated molded body having improved strength characteristics against axial compressive loads. [Solution] The laminated molded body of the present invention is a laminated molded body F in which fiber reinforcement layers AP containing a large number of aligned reinforcing fibers are arranged in multiaxial directions and laminated together, and the fiber reinforcement layers AP contain multiple reinforcing fiber groups consisting of a large number of aligned reinforcing fibers, and are set so that the fiber length directions of at least two reinforcing fiber groups intersect from opposite sides of the axial direction in which they are arranged.

Description

[Technical Field]

[0001] The present invention relates to a laminated molded article in which fiber-reinforced layers containing a large number of paralleled reinforcing fibers are arranged in multiaxial directions and laminated together. [Background technology]

[0002] Fiber-reinforced composite materials are made by combining reinforcing fiber materials with a matrix material. They are lightweight, highly rigid, and allow for a wide range of functional designs. Therefore, they are used in a wide range of fields, including aerospace, transportation, civil engineering and construction, and sports equipment. Fiber-reinforced plastics (FRPs), which combine reinforcing fiber materials such as carbon fiber and glass fiber with thermosetting resin materials, are particularly popular. Fiber-reinforced composite materials often use laminated molded products that have enhanced strength in multiple directions by stacking unidirectionally reinforced prepreg sheets and aligning each layer in multiple directions.

[0003] Laminated molded products have the problem that delamination is likely to occur because the reinforcement directions of each layer are different. In particular, when a thermosetting resin material such as an epoxy resin is used as the matrix, the thermosetting resin material generally has low toughness, which makes delamination likely to occur. For example, when an impact load or the like is applied to the laminated molded product, even if it appears to be fine on the outside, delamination often occurs inside the molded product, reducing the mechanical properties of the laminated molded product and making it more susceptible to fracture.

[0004] In response to these issues, Patent Document 1 describes that by laminating fiber reinforcement layers of 20 to 80 μm in thickness, in which reinforcing fiber material is dispersed in a thermosetting resin material that serves as a matrix, and forming a laminated molded body that includes a laminated portion in which the fiber reinforcement layers are laminated and a laminated portion in which a resin layer is laminated between the fiber reinforcement layers, the occurrence of delamination can be suppressed and good strength properties with improved impact resistance and fatigue life can be obtained.

[0005] Non-Patent Document 1 reports that when a tensile test is performed on a composite material in which aligned reinforcing fibers are dispersed in a resin matrix material, with the fiber length direction of the reinforcing fibers set to be inclined at a predetermined angle relative to the tensile load direction, the plasticity of the matrix resin causes the reinforcing fibers to rotate and reorient in the load direction, resulting in pseudo-ductility and increased rigidity after yielding. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Patent No. 5736560 [Non-patent literature]

[0007] [Non-Patent Document 1] JDFuller et al., 'Pseudo-ductility and damage suppression in thin ply CFRP angle-ply laminates', Composites: Part A 69(2015) 64-71 Summary of the Invention [Problem to be solved by the invention]

[0008] Patent Document 1 proposes improving impact resistance in the stacking direction by placing a resin layer between fiber-reinforced layers, but there is a need to improve strength characteristics in directions other than the stacking direction. Non-Patent Document 1 suggests that ductility in the load direction can be added by tilting the fiber length direction of the reinforcing fibers with respect to the tensile load.

[0009] On the other hand, in fiber-reinforced composite materials, when the reinforcing fibers are arranged so that their aligned direction is along the axial direction and a compressive load is applied in the axial direction, the reinforcing fibers are deformed so that they buckle, causing brittle fracture due to delamination between layers, resulting in a problem of reduced strength characteristics compared to other materials such as metals.

[0010] Therefore, an object of the present invention is to provide a laminated molded body having improved strength characteristics against axial compressive loads. [Means for solving the problem]

[0011] The laminated molded body according to the present invention is a laminated molded body in which fiber-reinforced layers containing a large number of aligned reinforcing fibers are arranged in multiple axial directions and laminated together, and the fiber-reinforced layers arranged in at least one axial direction contain a plurality of reinforcing fiber groups made up of a large number of aligned reinforcing fibers, and the fiber length directions of at least two of the reinforcing fiber groups are mutually perpendicular to the axial direction in which they are arranged. to From the other side At an intersection angle of 20° or less The fiber reinforcement layer is configured so that the fiber length directions of the reinforcing fiber groups intersect line-symmetrically with respect to the axial direction of the arrangement. The reinforcing fiber groups are made of prepreg sheets having a layer thickness of 10 μm to 80 μm, in which the reinforcing fibers are dispersed in a resin material that serves as a matrix, and the fiber reinforcement layer is integrally formed by laminating a plurality of the prepreg sheets so that the fiber length directions of the reinforcing fibers intersect. Furthermore, a resin layer is laminated between at least some of the layers of the fiber reinforcement layer. [Effects of the Invention]

[0012] The present invention has the above-described configuration, in which at least one axially arranged fiber-reinforced layer includes a plurality of reinforcing fiber groups each consisting of a large number of aligned reinforcing fibers, and the fiber length directions of at least two of the reinforcing fiber groups are set so as to intersect from opposite sides relative to the axial direction, resulting in a smaller decrease in initial elastic modulus compared to a unidirectional material in which the fiber length directions are aligned in the axial direction, and further, the reinforcing fiber groups intersecting from opposite sides in the axial direction are reoriented to widen the crossing angle in response to an axial compressive load, making it less likely to develop matrix cracks and interlayer delamination originating from such cracks. As a result, the fracture strain required for fracture due to a compressive load is increased, enabling improved compressive strength. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a schematic diagram showing an enlarged view of a part of a cross section of a laminated molded product F according to an embodiment of the present invention. [Figure 2] FIG. 2 is an explanatory diagram illustrating a stacking state of prepreg sheets that constitute a fiber reinforcement layer. [Figure 3] FIG. 2 is an explanatory diagram showing the arrangement of prepreg sheets when fiber reinforcement layers are laminated in four axial directions. [Figure 4] FIG. 10 is a schematic enlarged view showing a part of a cross section of a modified example of the laminated molded body. [Figure 5] FIG. 2 is an explanatory diagram showing a state in which resin layers are laminated between fiber reinforcement layers arranged in four axial directions. [Figure 6] FIG. 2 is an explanatory diagram of a laminated sheet as viewed from above. [Figure 7] 10A to 10C are explanatory views showing a process of cutting a laminated sheet to form a laminated tape. [Figure 8] FIG. 10 is an explanatory diagram of a case where a laminated molded body is produced using a prepreg tape in which reinforcing fibers are aligned in the longitudinal direction. [Figure 9] FIG. 10 is an explanatory diagram of a case where a laminated molded body is produced using a prepreg tape in which reinforcing fibers are aligned in the longitudinal direction. [Figure 10] 10 is a graph showing a method for calculating various parameters. [Figure 11A] 10 is a graph showing measurement results of a compression test on a uniaxially laminated compact. [Figure 11B] 10 is a graph showing measurement results of a compression test on a uniaxially laminated compact. DETAILED DESCRIPTION OF THE INVENTION

[0014] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the embodiments described below are preferred examples for carrying out the present invention, and therefore various technical limitations are imposed thereon. However, the present invention is not limited to these embodiments unless otherwise specified in the following description to the effect that the present invention is limited thereto.

[0015] 1 is a schematic diagram showing an enlarged cross section of a laminated molded product F according to an embodiment of the present invention. The laminated molded product F is molded by integrating and laminating fiber reinforcement layers AP1 to APn, each of which includes a plurality of reinforcing fiber groups made of a large number of aligned reinforcing fibers, in a multiaxially arranged manner.

[0016] Here, arranging the fiber reinforcement layers in a multi-axial direction means that, when the direction perpendicular to the stacking direction of the fiber reinforcement layers is taken as the axial direction, each fiber reinforcement layer is set to be offset by a different angle from the reference axial direction, and the layers are stacked so that they have different axial directions.

[0017] In this embodiment, the fiber reinforcement layer is arranged so that the fiber length directions of at least two reinforcing fiber groups intersect from opposite sides of the axial direction in which they are arranged, and the reinforcing fiber groups whose fiber length directions intersect and make up the fiber reinforcement layer are arranged at different angles along the axial direction, resulting in the fiber reinforcement layer being arranged in a multi-axial direction.

[0018] In addition, the fiber reinforcement layer, which has a group of reinforcing fibers whose fiber length directions intersect on opposite sides of the axial direction in which it is arranged, only needs to be arranged in at least one axial direction, and the axial direction in which it is arranged can be appropriately set depending on the compression characteristics, etc. of the laminated molded body.

[0019] The fiber-reinforced layer includes at least two groups of reinforcing fibers arranged in different fiber length directions, and each group of reinforcing fibers is arranged so as to overlap in layers in the lamination direction of the fiber-reinforced layer. For example, the reinforcing fiber groups can be formed by laminating at least two prepreg sheets, which are made of a resin matrix material in which aligned reinforcing fibers are dispersed.

[0020] Fig. 2 is an explanatory diagram illustrating the lamination state of prepreg sheets that constitute the fiber-reinforced layer. In the example shown in Fig. 2(a), two prepreg sheets P1 and P2 are laminated together, and prepreg sheet P1 is arranged so that the fiber length direction S1 of the aligned reinforcing fibers therein is offset by an angle of -θ with respect to the axial direction T of the fiber-reinforced layer. Prepreg sheet P2 is arranged so that the fiber length direction S2 of the aligned reinforcing fibers therein is offset by an angle of +θ with respect to the axial direction T. Therefore, in prepreg sheets P1 and P2, the reinforcing fibers are aligned so that the fiber length directions S1 and S2 intersect on opposite sides of the axial direction T.

[0021] 2(b), four prepreg sheets are stacked together, with two prepreg sheets P1 stacked together, with the fiber length direction of each prepreg sheet being offset by an angle of −θ with respect to the axial direction T, and two prepreg sheets P2 stacked together, with the fiber length direction of each prepreg sheet being offset by an angle of +θ with respect to the axial direction T. In this example, too, the fiber length directions of the prepreg sheets are set to intersect with each other from opposite sides of the axial direction when viewed from the stacking direction.

[0022] 2(c), four prepreg sheets are stacked alternately, with prepreg sheets P1 arranged such that the fiber length direction is offset by an angle of −θ with respect to the axial direction T and prepreg sheets P2 arranged such that the fiber length direction is offset by an angle of +θ with respect to the axial direction T. In this example, too, the fiber length directions of the prepreg sheets, as viewed from the stacking direction, are set to intersect with each other from opposite sides with respect to the axial direction.

[0023] As illustrated in Figure 2, in the fiber-reinforced layer, the fiber length directions of the reinforcing fiber groups are aligned so that they intersect from opposite sides of the axial direction, and it is preferable that the fiber length directions of the reinforcing fiber groups intersect line-symmetrically with respect to the axial direction.

[0024] The crossing angles of the fiber length directions of the reinforcing fiber groups with respect to the axial direction may be set asymmetrically at different angles, and are not limited to line symmetry.

[0025] Note that, as long as the fiber-reinforced layer can be configured by aligning the reinforcing fibers so that their fiber length directions cross each other from opposite sides, a reinforcing fiber group other than a prepreg sheet may be used, and there is no particular limitation. For example, by configuring a cross-laminated plate, an oblique laminate, or a pseudo-isotropic laminate, the fiber length directions of the reinforcing fibers can be configured so that they cross each other from opposite sides with respect to the axial direction.

[0026] Based on the findings described in Non-Patent Document 1, it is believed that by setting the fiber length direction of the reinforcing fibers to intersect the axial direction of the fiber-reinforced layer, misalignment due to rotation of the reinforcing fibers in the load direction occurs when a tensile load is applied in the axial direction. Therefore, the intersecting reinforcing fibers are reoriented to narrow the crossing angle, suppressing brittle fracture of the fiber-reinforced layer, increasing the fracture strain, and enabling increased tensile strength. It is believed that this rotation of the fiber-reinforced layer does not occur only in response to tensile loads. For example, it is believed that under compressive loads, the intersecting reinforcing fibers are reoriented to widen the crossing angle, suppressing brittle fracture of the fiber-reinforced layer, increasing the fracture strain, and ultimately improving compressive properties.

[0027] The crossing angle of the fiber length direction of the reinforcing fiber group with respect to the axial direction of the fiber-reinforced layer is preferably set to 20° or less, as viewed from the lamination direction, and more preferably 5° to 10°. If the crossing angle is greater than 20°, the angle difference between the compressive load applied in the axial direction and the fiber length direction becomes large, making it difficult to bear the compressive load and resulting in reduced compression characteristics.

[0028] Examples of reinforcing fibers used in the fiber-reinforced layer include high-strength, high-elasticity inorganic and organic fibers used in fiber-reinforced composite materials, such as carbon fibers, glass fibers, ceramic fibers, polyoxymethylene fibers, and aromatic polyamide fibers. A combination of these fibers may also be used, and there is no particular limitation on the fineness. Furthermore, fibers formed into a wide, thin reinforcing fiber sheet by a known air-spreading method (see, for example, Japanese Patent No. 4740131) may also be used.

[0029] Examples of resin materials that serve as the matrix of the fiber reinforcement layer include thermosetting resin materials such as epoxy resin, unsaturated polyester resin, vinyl ester resin, and phenolic resin, as well as thermoplastic resin materials such as polypropylene resin, polyamide resin, polyphenylene sulfide resin, polyetherimide resin, and polyether ether ketone resin, and polymer alloy resins made by mixing two or more of these thermoplastic resins.

[0030] The thickness of the prepreg sheets used in the fiber reinforcement layers is preferably 10 μm to 80 μm. By reducing the layer thickness, even when the fiber length direction of the prepreg sheets is arranged to cross the axial direction, the binding effect between the laminated prepreg sheets can prevent a decrease in the compressive strength of the fiber reinforcement layers.

[0031] If the prepreg sheet layer thickness is thinner than 10 μm, it becomes difficult to manufacture, stack, and handle the prepreg sheet itself during molding, which poses the problem of requiring a larger number of layers to obtain a structure of the same thickness.If the prepreg sheet layer thickness is thicker than 80 μm, the restraining effect achieved by the thin layering described above becomes smaller, resulting in a problem of reduced compression characteristics.

[0032] The prepreg sheet used for the fiber-reinforced layer can be manufactured using a known prepreg manufacturing device that impregnates a reinforcing fiber material with a thermosetting resin material or a thermoplastic resin material. When a thermoplastic resin material is used, the fiber-reinforced layer can be formed by using a prepreg sheet in which the reinforcing fiber material is bonded to a sheet-shaped thermoplastic resin material by heat fusion or the like. The prepreg sheet can be cut to an appropriate length and stacked so that the fiber length directions of the reinforcing fibers cross each other from opposite sides of the axial direction.

[0033] Fig. 3 is an explanatory diagram showing the arrangement of prepreg sheets when fiber reinforcement layers are laminated in four axial directions. In this example, two prepreg sheets shown in Fig. 2(a) are overlapped to form a fiber reinforcement layer, and four fiber reinforcement layers AP1 to AP4 are laminated in four axial directions, shifted by 90°.

[0034] In each fiber-reinforced layer, the fiber length directions of the reinforcing fibers of the prepreg sheets are set to a crossing angle of ±5° with respect to the axial direction, and in fiber-reinforced layer AP1, the reinforcing fibers are aligned with their fiber length directions shifted by 40° and 50° with respect to the 45° axial direction. Therefore, the fiber length directions of the reinforcing fibers of the prepreg sheets are set to cross each other from opposite sides with respect to the axial direction.

[0035] In the fiber reinforcement layer AP2, the reinforcing fibers of the prepreg sheet are aligned with their fiber length directions shifted by -5° and 5° relative to the axial direction of 0°, and the fiber length directions of the reinforcing fibers of the prepreg sheet are set to intersect with each other from opposite sides relative to the axial direction.

[0036] In the fiber reinforcement layer AP3, the reinforcing fibers of the prepreg sheet are aligned with their fiber length directions shifted at -50° and -40°, respectively, relative to the axial direction of -45°, and the fiber length directions of the reinforcing fibers of the prepreg sheet are set to intersect with each other from opposite sides relative to the axial direction.

[0037] In the fiber reinforcement layer AP4, the reinforcing fibers of the prepreg sheet are aligned with their fiber length directions shifted by 85° and 95° relative to the 90° axial direction, and the fiber length directions of the reinforcing fibers of the prepreg sheet are set to intersect with each other from opposite sides relative to the axial direction.

[0038] By repeatedly stacking and integrating these fiber reinforcement layers stacked in four axial directions, a laminated molded body can be obtained in which the fiber length directions of the reinforcing fibers of the prepreg sheets are arranged so that they cross each other from opposite sides in each axial direction.

[0039] 4 is a schematic diagram showing an enlarged cross section of a modified example of the laminated molded body. In this example, the laminated molded body F' has resin layers TR1-TRm laminated between at least some of the fiber reinforcement layers AP1-APn, and laminating the resin layers can improve strength properties such as impact resistance.

[0040] The resin material used for the resin layer is preferably a thermoplastic resin material, and can be used in the form of fine powder, nonwoven fabric, mesh, film, sheet, etc. The resin layer may also contain fine powder, sheet, metal mesh, metal foil, etc. of nanomaterials such as CNT (carbon nanotube) and graphene, and is not particularly limited as long as it can be integrally molded.

[0041] The thickness of the resin layer is preferably set to 1 μm to 80 μm. If the thickness of the resin layer is thinner than 1 μm, there is a problem that manufacturing is difficult, and if it is thicker than 80 μm, there is a problem that the entire molded article becomes thick and the strength of the resin layer itself is lower than that of the fiber reinforced layer, resulting in a decrease in the compression characteristics of the entire molded article.

[0042] Fig. 5 is an explanatory diagram showing a state in which resin layers are laminated between fiber reinforcement layers arranged in four axial directions. In this example, as shown in Fig. 3, resin layers TR1 to TR4 are laminated between each of the fiber reinforcement layers AP1 to AP4 arranged in four axial directions.

[0043] By repeatedly stacking and integrating layers that combine such fiber reinforcement layers and resin layers, a laminated molded body can be obtained in which the fiber length directions of the reinforcing fiber groups are arranged so that they cross each other from opposite sides in any axial direction.

[0044] In the above example, a resin layer is disposed for each fiber reinforcement layer, but it may be disposed for every other layer, and is not particularly limited.

[0045] The laminated molded body preferably has an overall fiber volume fraction (Vf) of 30% to 80%, more preferably 50% to 70%. If Vf is less than 30%, the fiber reinforcement effect of the laminated molded body cannot be fully obtained, and if Vf exceeds 80%, the resin amount becomes so small that voids (air spaces) are easily formed in the fiber reinforced layer, deteriorating the mechanical properties of the laminated molded body.

[0046] A laminated molded body can be produced by cutting prepreg sheets to a predetermined size, stacking them one by one to form a fiber-reinforced layer, and then laminating and integrating multiple fiber-reinforced layers. Alternatively, a laminated sheet can be produced in advance by stacking multiple prepreg sheets so that the fiber length directions of the reinforcing fibers intersect, cutting the laminated sheet to a predetermined size, and integrating and integrating multiple cut laminated sheets. A laminated molded body can also be produced in a similar manner by stacking multiaxial sheets or woven fabrics, such as non-crimp fabrics, in which fiber bundles are oriented in two or more axes, placing them in a mold, etc., and then injecting resin.

[0047] FIG. 6 is an explanatory diagram of a laminate sheet as viewed from above. In this example, two prepreg sheets P1 and P2 are stacked to form a laminate sheet S1. The prepreg sheet P1 is configured so that the fiber length direction of the reinforcing fibers is offset counterclockwise by an angle of +θ when the vertical direction is 0°, and the prepreg sheet P2 is configured so that the fiber length direction of the reinforcing fibers is offset clockwise by an angle of −θ. Therefore, when the prepreg sheets P1 and P2 are stacked together to form a laminate sheet, a laminate sheet can be produced in which the fiber length directions of the reinforcing fibers are set to intersect with each other on opposite sides of the vertical direction. In this case, the vertical direction corresponds to the axial direction in which the laminate sheet is arranged.

[0048] In this example, the axial direction of the laminated sheet is set to the direction of the axis of symmetry along which the fiber length directions of the reinforcing fibers of the prepreg sheets intersect linearly symmetrically, but it is not limited to the axis of symmetry. As long as the axial direction is set between the fiber length directions of the intersecting reinforcing fibers of the prepreg sheets, the fiber length directions can be set to intersect from opposite sides of the axial direction.

[0049] The laminated sheet can also be formed by overlapping two or more prepreg sheets, and the number of prepreg sheets is not particularly limited as long as the fiber length directions of the reinforcing fibers in at least two prepreg sheets are set to intersect. Furthermore, when a resin layer is laminated between the fiber-reinforced layers shown in Fig. 4, a laminated molded product including a resin layer can be efficiently produced by pre-producing the laminated sheet by overlapping a resin sheet on the prepreg sheet to be laminated.

[0050] When laminating a laminated molded body into a three-dimensional shape, automated lamination techniques such as automated fiber placement (AFP) and automated tape laying (ATL) have been developed (see, for example, Japanese Patent No. 6935620), and for these lamination techniques, a laminated tape obtained by cutting the above-mentioned laminated sheet into tape-like shapes of a predetermined width can be used.

[0051] Fig. 7 is an explanatory diagram showing the process of cutting a laminated sheet to form a laminated tape. As shown in Fig. 6, the laminated sheet S1 is formed by laminating two prepreg sheets P1 and P2, and the laminated sheet S1 can be cut to a predetermined width along the axial direction C to obtain a laminated tape U1. When cutting the laminated sheet, a cutting device such as a slitter is used to cut the laminated sheet, allowing multiple laminated tapes to be cut simultaneously and processed efficiently.

[0052] In this case, the cutting axial direction C can be set between the fiber length directions of the intersecting reinforcing fiber groups of the laminated sheet so that the fiber length directions of the reinforcing fiber groups intersect from opposite sides of the axial direction.

[0053] The obtained laminated tape is set so that the fiber length directions of the reinforcing fiber groups intersect, and by stacking the laminated tape so that the tape length direction is along the axial direction to form a fiber reinforcement layer, the fiber length directions of the reinforcing fiber groups can be aligned so that they intersect from opposite sides of the axial direction in which they are arranged.

[0054] A laminated sheet can also be manufactured using unidirectional prepreg tape in which reinforcing fibers are aligned in the longitudinal direction. Fig. 8 is a schematic diagram of a manufacturing apparatus for forming a laminated sheet using unidirectional prepreg tape, and Fig. 9 is an explanatory diagram showing the lamination process in Fig. 8.

[0055] In this example, multiple prepreg tapes are supplied in parallel so that they are oblique at a predetermined angle to the conveyance direction relative to the surface of a substrate such as conveyed release paper or release film, and are stacked so that the fiber length direction of the prepreg tapes intersects the axial direction (conveyance direction). The substrate conveying mechanism 20 includes an unwinding roll 21 that pays out the sheet-like substrate R, a stage 22 that supports the conveyed substrate R, and a take-up roll 23 that takes up the substrate R, and conveys the substrate R in a predetermined conveyance direction F1. Above the stage 22, there are slitters 24 that are arranged on both side edges of the substrate R and cut the prepreg tape PT along both side edges.

[0056] A plurality of tape supply mechanisms 101 to 105 are arranged in parallel above the stage 22. Each tape supply mechanism includes a winding roll 11 that winds out the prepreg tape PT, a pressure roller 12 that presses the unwound prepreg tape PT against the substrate R, and a cutter 13 that cuts the unwound prepreg tape PT. Each tape supply mechanism is movable in the width direction of the prepreg tape PT, and operates so that if the tape supply mechanism deviates from one side edge of the substrate R, it moves to the other side edge.

[0057] As shown in Fig. 9, the base material R is transported along both side edges, and the slitter 24 is arranged along both side edges. The prepreg tape PT is supplied to the surface of the base material R in a supply direction F2 that is oblique counterclockwise at an angle θ to the base material transport direction F1, as shown by the dotted line. The prepreg tapes PT supplied from each tape supply mechanism are arranged parallel to each other and are in close contact with each other to cover the surface of the base material R without any gaps (Fig. 9(a)).

[0058] The prepreg tape PT is supplied obliquely in a supply direction F2 relative to the conveyance direction of the base material R, so that the prepreg tape PT gradually comes off to the outside of the right edge of the base material R, starting from the rightmost prepreg tape PT (FIG. 9(b)). Therefore, by cutting the prepreg tape PT when it comes off the right edge of the base material R, moving the tape supply mechanism to the leftmost position, and supplying the prepreg tape PT obliquely, the prepreg tape PT can be continuously adhered to the surface of the base material R without any gaps (FIG. 9(c)).

[0059] The prepreg tape PT adhered to the surface of the substrate R is cut by a slitter 24, and the substrate R with the one-directional prepreg tape PT tightly adhered to both side edges so as to intersect at an angle θ is taken up on a take-up roll 23.

[0060] In the next step, the substrate R to which the unidirectional prepreg tape PT has been tightly adhered is laminated with more unidirectional prepreg tape PT tightly adhered with no gaps in a supply direction that is oblique clockwise at an angle θ to the conveying direction during conveyance. To laminate the prepreg tape PT, multiple tape supply mechanisms can be arranged in parallel, similar to the tape supply mechanism described above, and the prepreg tape PT can be supplied and laminated at an angle θ to the clockwise direction relative to the conveying direction.

[0061] In this way, a laminated sheet can be formed in which the unidirectional prepreg tapes PT are closely laminated on the surface of the base material R so as to cross each other from opposite sides in the conveyance direction.

[0062] Furthermore, by arranging a tape supply mechanism that is obliquely clockwise and a tape supply mechanism that is obliquely counterclockwise on the transport path of the substrate R, prepreg tapes PT can be sequentially supplied to the substrate R being transported so that they intersect from opposite sides of the transport direction, and laminated sheets can be continuously produced in which prepreg tapes PT from two directions are tightly stacked so that they intersect with each other. [Example]

[0063] <About compression testing> Using a precision universal testing machine (Shimadzu Corporation), a rectangular molded plate (78 mm long x 12.5 mm wide x 2 mm thick) was placed so that the compressive load direction coincided with the axial direction, and a compression test was performed in accordance with JIS K 7018. Based on the test results obtained, the compressive strength (MPa), elastic modulus (GPa), and fracture strain (%) were determined.

[0064] <Calculation of various parameters> The yield stress, yield strain, and ductile strain were calculated based on the calculation method shown in Non-Patent Document 1. Fig. 10 is a graph showing the calculation method for various parameters, with the compressive stress (MPa) on the vertical axis and the strain (%) on the horizontal axis.

[0065] Yield stress (σ Y ) and yield strain (ε Y), the coordinates of the intersection of the line L2 (0.1% offset line: shown in dotted line) obtained by shifting the line L1 (shown in dotted line) indicating the initial elastic modulus in the X-axis direction by 0.1% and the stress-strain curve (shown in solid line) obtained in the experiment are defined as the yield stress (σ Y ) and yield strain (ε Y ) was calculated.

[0066] Ductile strain ((ε d ) Based on the fracture strain and stress at fracture (compressive strength) obtained in the experiment, the strain value on the line L1, which indicates the initial elastic modulus corresponding to the stress at fracture, was calculated, and the difference between the calculated strain value and the fracture strain value was calculated as the ductile strain.

[0067] <Production of laminated sheets and laminated molded products> 〇Matrix resin An epoxy resin material was prepared as a matrix resin material by mixing and stirring the following components. The density of the prepared epoxy resin material was 1.20 g / cm 3 It was. Bisphenol A epoxy resin (jER828: manufactured by Mitsubishi Chemical Corporation) 40 parts by weight Bisphenol A epoxy resin (jER1001: manufactured by Mitsubishi Chemical Corporation) 60 parts by weight Accelerator (DCMU99: manufactured by Hodogaya Chemical Co., Ltd.) 2 parts by weight Hardener (DICY15: manufactured by Mitsubishi Chemical Corporation) 5 parts by weight The prepared epoxy resin material was applied to the upper surface of release paper (manufactured by Lintec Corporation) with a weight of 10.8 g / m 2 The resin sheet was prepared by coating with the resin in a width of 320 mm.

[0068] Reinforcing fiber As the reinforcing fiber, six carbon fiber bundles (TR50S15L: manufactured by Mitsubishi Chemical Corporation) were arranged at intervals of 50 mm, and were spread to a width of 50 mm per bundle using a fiber spreader (manufactured by Hokushin Co., Ltd.) to form a 300 mm wide spread fiber sheet (fiber basis weight: 20 g / m 2 ) was created.

[0069] Prepreg sheet The produced spread fiber sheet and resin sheet were stuck together, and the matrix resin was impregnated into the spread fiber sheet while heating and pressurizing with a prepreg production device (manufactured by Hokushin Co., Ltd.), to produce a prepreg sheet. The produced prepreg sheet had a thickness of 0.02 mm and a fiber volume content of 55%.

[0070] Laminated molded body The prepared prepreg sheets were laminated in a uniaxial direction by hand layup in the lamination configuration shown in Table 1, and then molded into a flat uniaxial laminate molded body using an autoclave (manufactured by Ashida Manufacturing Co., Ltd.) at 130°C for 2 hours. [Table 1]

[0071] In Examples 1 to 3, the prepreg sheets were stacked with an alternating offset of ±5°, ±10°, and ±15° relative to the axial direction, respectively, so that the fiber length direction of the prepreg sheets crossed the axial direction. On the other hand, in Comparative Example 1, the prepreg sheets were stacked with their fiber length direction aligned with the axial direction, and in Comparative Example 2, a laminate sheet with a layer thickness of 0.24 mm, in which 12 prepreg sheets were stacked in one direction, was stacked with an alternating offset of ±5° relative to the axial direction.

[0072] The prepreg sheets were then hand-laid in four directions using the lamination configuration shown in Table 2, and processed in the same manner as the uniaxial laminated molded body to form a flat quasi-isotropic laminated molded body. The obtained molded body was subjected to a 0° compression test to evaluate its mechanical properties. [Table 2]

[0073] In Example 4, the prepreg sheets are alternately stacked with a deviation of ±5° relative to the four-axis direction, in Example 5, the prepreg sheets are alternately stacked with a deviation of ±10° relative to the four-axis direction, and in Example 6, the prepreg sheets are stacked with a deviation of ±15° relative to the four-axis direction. Therefore, in each Example, the prepreg sheets are stacked so that the fiber length direction of the prepreg sheets crosses the axial direction. On the other hand, in Comparative Example 3, the prepreg sheets are stacked so that the fiber length direction coincides with the four-axis direction.

[0074] <Evaluation of mechanical properties of laminated molded body> 11A and 11B show the measurement results of the compression test on the uniaxially laminated compact shown in Table 1. In Fig. 11A and 11B, the vertical axis represents the compressive load (MPa) and the horizontal axis represents the compressive strain (%), with the transition of the compressive strain shown by a thick solid line.

[0075] Fig. 11A(a) shows Comparative Example 1, Fig. 11A(b) shows Example 1, Fig. 11B(a) shows Example 2, and Fig. 11B(b) shows Example 3. Data on compression characteristics calculated based on the measurement results are shown in Table 3. [Table 3]

[0076] Comparing Examples 1 to 3 with Comparative Example 1, the modulus of elasticity decreased as the crossing angle increased, and the decrease rates relative to Comparative Example 1 were approximately 1.7%, approximately 9.4%, and approximately 18% at crossing angles of 5°, 10°, and 15°, respectively. It can be seen that the decrease in modulus of elasticity was smaller when the crossing angles were 5° and 10°.

[0077] On the other hand, the fracture strain tended to increase as the crossing angle increased. The reduction rates of compressive strength compared to Comparative Example 1 were approximately 3.9%, approximately 4.5%, and approximately 7.6% at crossing angles of 5°, 10°, and 15°, respectively, confirming that the increase in fracture strain was smaller than the reduction rate of elastic modulus. In particular, when the crossing angles were 5° and 10°, the reduction rate of compressive strength was within 5%, indicating that the compressive strength was almost equivalent to that of Comparative Example 1.

[0078] Furthermore, when the crossing angle was 15°, there was a difference of about 10% between the rate of decrease in elastic modulus and compressive strength, and it was confirmed that despite a large decrease in elastic modulus, the effect of suppressing the decrease in compressive strength was confirmed by the increase in breaking strain. The tendency for the breaking strain to increase as the crossing angle increased is thought to be due to the rotation of the orientation of the reinforcing fibers due to the axial compressive load.

[0079] Comparing Example 1 and Comparative Example 2, it is found that in Comparative Example 2, where the fiber-reinforced layer is thick, the fracture strain is small, the compressive strength is reduced, and the rotation of the reinforcing fiber orientation increases as the layer thickness decreases. It is believed that the thinner the reinforcing fiber layer, the stronger the constraining effect between adjacent layers and the higher the damage tolerance, which in turn increases the degree of rotation of the reinforcing fiber orientation. In other words, it is believed that by reducing the thickness of the fiber-reinforced layer that constitutes the laminated molded product, the occurrence of initial damage such as cracks in the matrix resin and the resulting delamination is suppressed, and the tolerance for rotation of the reinforcing fiber orientation increases, resulting in a larger fracture strain.

[0080] Next, for the quasi-isotropic laminated molded body, data on the compression characteristics calculated based on the measurement results of Examples 4 to 6 and Comparative Example 3 are shown in Table 4. [Table 4]

[0081] Comparative Example 3 has a laminated structure of a typical quasi-isotropic laminated body, in which the angles of the four axial directions of lamination are 0°, ±45°, and 90°, and the lamination ratio of each axis is often set to 25%. In contrast, Examples 4 to 6 are laminated in the four axial directions of Comparative Example 3 by arranging fiber reinforcement layers formed by reinforcing fiber groups crossing at a predetermined crossing angle from opposite sides of the axial directions, and as with Examples 1 to 3, the decrease in elastic modulus is suppressed and the breaking strain is increased. However, when Examples 4 to 6 are compared with Comparative Example 3, it was confirmed that there was almost no change in the elastic modulus, while the breaking strain was increased.

[0082] The fact that the decrease in elastic modulus remains almost unchanged is thought to be largely due to the influence of the constraining effect of the thinner fiber-reinforced layers. Furthermore, the constraining effect of adjacent fiber-reinforced layers tends to be stronger as the angle between layers increases. For example, when a 90° layer and a 0° layer are adjacent, the constraining effect is greater than when a 90° layer and a 45° layer are adjacent. This is because, when a load is applied to a 90° layer in a direction perpendicular to the reinforcing fibers (the 0° direction), a larger load can be applied to the 0° layer than to the 45° layer, since the fiber length direction of the reinforcing fibers in the adjacent layer is the same as the load direction, resulting in less strain in the 90° layer.

[0083] In Comparative Example 3, the angle between adjacent layers is always constant at 45° and is uniform in the plate thickness direction. On the other hand, in Example 4, in addition to the 45° angle in the axial direction, the prepreg sheets are misaligned at an angle of 10° within the fiber reinforced layers, resulting in an overall interlayer angle of 55°, which is larger than that of Comparative Example 3. Therefore, it is thought that the restraint effect within the fiber reinforced layers and the restraint effect due to the larger adjacent angle between layers result in a high restraint effect throughout the laminated molded body, resulting in a larger fracture strain.

[0084] It can also be seen that the compressive strength of Examples 4 to 6 is improved compared to Comparative Example 3. The rate of increase in compressive strength is approximately 7.3% when the crossing angle is 5°, approximately 8.3% when it is 10°, and approximately 0.7% when it is 15°, and it is thought that in the case of crossing angles of 5° and 10°, the rigidity of the fiber reinforced layer is maintained at a high level in view of the compression characteristics of the prepreg sheet, resulting in improved compressive strength.

[0085] As shown in Comparative Example 3, in the case of a typical quasi-isotropic laminate, the breaking strain against the compressive load is smaller than those in Examples 4 to 6. It is believed that such compressive characteristics are caused by buckling and kinking of the reinforcing fibers due to the compressive load, making the breaking strain extremely smaller than that against the tensile load.

[0086] In contrast, when a compressive load in the 0° direction is applied as shown in Examples 4 to 6, the absence of a fiber reinforcement layer with the fiber length direction set in the same direction as the load direction delays the occurrence of initial damage such as buckling or kinking, resulting in a larger fracture strain and, as a result, improved compressive strength and suppressed brittle damage behavior. [Industrial Applicability]

[0087] As described above, the laminated molding of the present invention has a structure in which fiber-reinforced layers are stacked together, in which the fiber length directions of the reinforcing fiber groups are set so as to intersect with each other on opposite sides of the axial direction in which they are arranged. Therefore, compared with conventional laminated moldings, the compression characteristics are improved, making it possible to use it as a structural material, and it is expected to be widely used as other industrial materials. [Explanation of symbols]

[0088] F···Laminated molded body, AP···Fiber reinforcement layer, P···Prepreg sheet, S···Fiber length direction, T···Axial direction, TR···Resin layer

Claims

1. A laminated molded body in which fiber reinforcement layers containing a large number of aligned reinforcing fibers are arranged in multiaxial directions and laminated together, wherein the fiber reinforcement layers arranged in at least one axial direction contain multiple reinforcing fiber groups consisting of a large number of aligned reinforcing fibers, and the fiber length directions of at least two of the reinforcing fiber groups are set to intersect with each other from opposite sides of the axial direction at an angle of 20° or less.

2. A laminated molded body as described in Claim 1, wherein the fiber reinforcement layer is configured so that the fiber length direction of the reinforcing fiber group intersects linearly symmetrically with respect to the axial direction in which it is arranged.

3. A laminated molded body as described in claim 1 or 2, wherein the group of reinforcing fibers consists of a prepreg sheet having a layer thickness of 10 μm to 80 μm in which the reinforcing fibers are dispersed in a resin material that serves as a matrix, and the fiber reinforcement layer is integrally formed by stacking multiple prepreg sheets so that the fiber length directions of the reinforcing fibers cross.

4. A laminated molded body as described in claim 1 or 2, in which a resin layer is laminated between at least some of the layers of the fiber reinforcement layer.

5. A laminated sheet that is arranged in the axial direction to produce the laminated molded body described in claim 1 or 2, and is integrally formed by stacking multiple prepreg sheets with a layer thickness of 10 μm to 80 μm, in which the reinforcing fibers are dispersed in a resin material that serves as a matrix, so that the fiber length direction of the reinforcing fibers intersects with the axial direction.

6. A laminated sheet as described in claim 5, having a resin layer laminated thereon.

7. A laminated tape formed by cutting the laminated sheet described in claim 5 to a predetermined width along the axial direction.

8. A method for manufacturing a laminated sheet that is arranged in the axial direction to produce the laminated molded body described in claim 1 or 2, comprising stacking multiple prepreg sheets with a layer thickness of 10 μm to 80 μm, in which a large number of aligned reinforcing fibers are dispersed in a resin material that serves as a matrix, so that the fiber length direction of the reinforcing fibers intersects with the axial direction, to form a sheet.

9. A method for manufacturing a laminated sheet as described in Claim 8, in which a resin sheet is overlapped at least partially between the overlapping prepreg sheets.

10. A method for manufacturing a laminated tape that is arranged in an axial direction to produce a laminated molded product as described in claim 1 or 2, comprising stacking multiple prepreg sheets with a layer thickness of 10 μm to 80 μm, in which a large number of aligned reinforcing fibers are dispersed in a resin material that serves as a matrix, so that the fiber length direction of the reinforcing fibers crosses the axial direction, and laminating them together to form a sheet, and then cutting the laminated sheet to a predetermined width along the axial direction.

11. A method for manufacturing a laminated tape as described in Claim 10, in which a resin sheet is overlapped at least partially between the overlapping prepreg sheets.

12. A method for manufacturing a laminated molded body, which comprises cutting the laminated sheet described in claim 5 to a predetermined size, stacking the cut laminated sheets in a multi-axial direction, and integrally molding the stacked laminated sheets.

13. A method for manufacturing a laminated molded body, which comprises cutting the laminated tape described in claim 7 to a predetermined length, stacking the cut laminated tapes so that their longitudinal directions are multi-axial, and integrally molding the stacked laminated tapes.

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